Abstract
PURPOSE OF REVIEW: Given the potential for exogenous hormones to influence risk and course of MS, this narrative review aims to summarize current knowledge from observational and interventional studies of exogenous hormones in humans with MS. RECENT FINDINGS: Large randomized clinical trials for combined oral contraceptives and estriol both show modest effect on inflammatory activity, with the latter showing potential neuroprotective effect. After fertility treatment, large actively treated cohorts have not confirmed any elevated risk of relapse. Preclinical data suggest that androgens, selective estrogen receptor modulators (SERMs), and selective androgen receptor modulators (SARMs) may be neuroprotective but clinical data are lacking. Gender affirming treatment, particularly estrogen in trans-women, could possibly be associated with elevated risk of inflammation. For women with MS entering menopause, hormone therapy appears safe during the appropriate menopausal window, but its long-term effects on neuroprotection are unknown. Exogenous hormones, used in varied doses and for diverse indications, have variable effects on MS risk, inflammatory activity, and neuroprotection. Large randomized trials are needed before it is possible to determine the true effect of exogenous hormones in a condition as complex as MS.